The present invention is related generally to the field of orthodontics, and more particularly to a system and a method for gradually repositioning teeth.
A fundamental objective in orthodontics is to realign a patients teeth to positions where the teeth function optimally and aesthetically. Typically, appliances such as braces are applied to the teeth of the patient by a treating orthodontist. Each appliance exerts continual forces on the teeth which gradually urge the teeth toward their ideal positions. Over a period of time, the orthodontist adjusts the appliances to move the teeth toward their final destination.
The process of attaching the braces to teeth is tedious and painful. Additionally, each visit to the orthodontist is time consuming and expensive. The process is further complicated by uncertainties in determining a final arrangement for each tooth. Generally, the final tooth arrangement is determined by the treating orthodontist who writes a prescription. Traditionally, the prescription is based on the orthodontist""s knowledge and expertise in selecting the intended final position of each tooth and without a precise calculation of forces being exerted on the teeth when they contact each other.
The present invention includes a system, apparatus and computer-implemented method for arranging a computer model of teeth.
According to one implementation, the method includes generating an archform representing an arrangement of teeth; placing a plurality of teeth according to the archform; determining a differential distance between each tooth and its neighbors; and moving each tooth according to the differential distance.
According to one aspect, the method includes repeating the determining and moving steps according to a function of at least one of the differential distances.
According to one aspect, the method includes repeating the determining and moving steps when the sum of differential distances for the plurality of teeth exceeds a predetermined threshold, thereby producing a final digital data set.
According to one aspect, the method includes modifying the archform according to a curve of Spee.
According to one aspect, the placing step includes defining an attachment point for each tooth; and placing each tooth so the archform passes through the attachment point of the tooth.
According to one aspect, the determining step includes determining a first distance between a selected tooth and a first tooth that is adjacent to the selected tooth; determining a second distance between the selected tooth and a second tooth that is adjacent to the selected tooth; and calculating a difference between the first and second distances.
According to one aspect, the first and second distances are the minimum distances between the teeth.
According to one aspect, the method includes defining distal and mesial measurement points for each tooth; and measuring the first and second distances between the measurement points.
According to one aspect, the moving step includes translating each tooth so that the attachment point of the tooth remains on the archform.
According to one aspect, the method includes translating each tooth a distance proportional to the projection of the differential distance of the tooth upon a tangent to the archform at the attachment point of the tooth.
According to one aspect, the method includes moving at least one of the teeth in response to input from a user.
According to one aspect, the method includes generating an initial final digital data set based on a masticatory system of a patient; generating at least one intermediate digital data set based on the initial digital data set and the final digital data set; and producing an incremental adjustment appliance based on each intermediate digital data set.
According to one implementation, the system includes a processor; a display device coupled to the processor; and a data storage device coupled to the processor, the data storage device storing instructions operable to cause the processor to: generate an archform representing an arrangement of teeth; place a plurality of teeth according to the archform; determine a differential distance between each tooth and its neighbors; move each tooth according to the differential distance; and repeat the determining and moving steps according to a function of at least one of the differential distances when the sum of differential distances for the plurality of teeth exceeds a predetermined threshold.
The method also includes generating a model of the teeth; and adjusting teeth position in the model by following a prescription. The method further includes generating a model of the teeth, the model having a visual appearance; and adjusting teeth position in the model until the visual appearance of the model is satisfactory. The model can be based on an abstract model of idealized teeth placement. The abstract model can be specified by one or more arch forms, or can be specified using one or more features associated with the teeth. The teeth position can be customized to the patient""s teeth.
In another aspect, a system for generating one or more appliances for a patient includes a processor; a display device coupled to the processor; a data storage device coupled to the processor; a scanner coupled to the processor for providing data to model the masticatory system; means for defining a fit between a set of upper and lower teeth in a masticatory system of the patient; and a dental appliance fabrication machine coupled to the processor for generating the appliances in accordance with the fit of the teeth.
Advantages of the invention include one or more of the following. When a prescription or other final designation is provided, a computer model can be generated and manipulated to match the prescription. The prescription may be automatically interpreted in order to generate an image as well as a digital data set representing the final tooth arrangement.
In still another aspect, methods according to the present invention provide for fabricating a plurality of dental incremental position adjustment appliances. Said methods comprise providing an initial digital data set, a final digital data set, and producing a plurality of successive digital data sets representing the target successive tooth arrangements, generally as just described. The dental appliances are then fabricated based on at least some of the digital data sets representing the successive tooth arrangements. Preferably, the fabricating step comprises controlling a fabrication machine based on the successive digital data sets to produce successive positive models of the desired tooth arrangements. The dental appliances are then produced as negatives of the positive models using conventional positive pressure or vacuum fabrication techniques. The fabrication machine may comprise a stereolithography or other similar machine which relies on selectively hardening a volume of non-hardened polymeric resin by scanning a laser to selectively harden the resin in a shape based on the digital data set. Other fabrication machines which could be utilized in the methods of the present invention include tooling machines and wax deposition machines.
In still another aspect, methods of the present invention for fabricating a dental appliance comprise providing a digital data set representing a modified tooth arrangement for a patient. A fabrication machine is then used to produce a positive model of the modified tooth arrangement based on the digital data set. The dental appliance is then produced as a negative of the positive model. The fabrication machine may be a stereolithography or other machine as described above, and the positive model is produced by conventional pressure or vacuum molding techniques.
In a still further aspect, methods for fabricating a dental appliance according to the present invention comprise providing a first digital data set representing a modified tooth arrangement for a patient. A second digital data set is then produced from the first digital data set, where the second data set represents a negative model of the modified tooth arrangement. The fabrication machine is then controlled based on the second digital data set to produce the dental appliance. The fabrication machine will usually rely on selectively hardening a non-hardened resin to produce the appliance. The appliance typically comprises a polymeric shell having a cavity shape to receive and resiliently reposition teeth from an initial tooth arrangement to the modified tooth arrangement.